World Elephant Day, National Dog Day and Southern Hemisphere Hoodie-Hoo Day are just a few of the celebratory days you can enjoy this month.

[skipwords]It starts with Earth Day on April 22. What follows every spring and summer is a calendar jam-packed with eco-themed and animal rights holidays. But where do these special days come from? Who creates them and why? Do they all serve good causes, or are some of them just for fun? Sometimes you need to dig to find the answers — but knowing the story behind the occasion can help you to know which ones are worth celebrating.

Government-supported holidays

Like Labor Day or Thanksgiving, some eco-holidays are established by government decree, often after being initiated by a private group or organization. Take Global Tiger Day (July 29) for example. One of the newer eco-themed holidays on the calendar, Global Tiger Day was first proposed in 2010 by the 13 nations where tigers still exist and was created to promote awareness about tiger conservation. The governments of Russia, India, Bangladesh and other nations officially recognized the day, which helped make the event more effective. "Government ownership of Global Tiger Day means that it enters the official calendar and is marked by the relevant ministries, NGOs, community partners and civil society," says Barney Long, tiger program manager for the World Wildlife Fund.

The multi-nation acceptance of Global Tiger Day also means there is no overall body shepherding the event or offering a single thematic message to promote it. There isn't even an official Global Tiger Day website or logo. "Each government marks Global Tiger Day in a way that is relevant to its national audiences," Long says.

A few eco-themed days have a different governmental body behind them: the United Nations. World Rivers Day (Sept. 30 this year) started in Canada as a day to clean up rivers in British Colombia. It expanded to become Canadian Rivers Day, then World Rivers Day. It has since been endorsed by several U.N. agencies. Clean up the World Weekend (Sept. 14-16 this year) was started by Ian Kiernan as a one-nation event in Australia in 1990. It went international three years later and is now held in conjunction with the United Nations Environment Programme (UNEP). This year will be the 20th annual worldwide event.

Other events are sponsored by a single country. World Elephant Day, which was held for the first time this year on Aug. 12, was established by the Elephant Reintroduction Foundation, an organization founded under a royal initiative of Thailand's Queen Sirikit. The foundation's goal is to acquire captive elephants and reintroduce them to the wild in protected forest habitats, and fundraising efforts support those efforts. The day was a trending topic on Twitter recently, thanks in no small part to actor William Shatner who tweeted about his role narrating a documentary the foundation released online.

Private groups, public days

Some eco-themed events are started by companies, activist groups or even individuals. Global Wind Day (June 15) is organized by two industry associations, the European Wind Energy Association and Global Wind Energy Council. National Dog Day, coming up on Aug. 26, was established in 2004 by pet lifestyle expert Colleen Paige, who also created events like National Mutt Day, National Farm Animals Day, National Walk Your Dog Week and National Specially-abled Pets Day. Neither Paige nor her Animal Miracle Foundation, which organizes the various events, responded to requests to comment for this article.

One company, Wellcat Herbs, took things one step further and created more than 80 copyrighted, tongue-in-cheek holidays that the company offers to license to anyone who wants to make use of them. This month's options include Sneak Some Zucchini onto your Neighbor's Porch Day (Aug. 8), Bad Poetry Day (Aug. 18) and Southern Hemisphere Hoodie-Hoo Day (Aug. 22), "the day to go outdoors at high noon and yell 'Hoodie-Hoo' to chase winter and make ready for spring."

Some events belong to the people

Strong personalities and passionate people help keep events going past their inaugural dates.

"Unless there is some group with the responsibility to kick-start these kinds of things — veteran's groups for Veteran's Day and Memorial Day, for example — not much happens, typically," says Kathleen Rogers, president of the Earth Day Network. But once things get going, eco-holidays can become attached to a certain date and repeat year after year. The original Earth Day in 1970 was intended as environmental teach-in, and founder Gaylord Nelson wanted to schedule the event on a day when students would be most likely to attend. April 22 fit the bill that first year, and it continued on that date as teachers added it to their calendars.

"It stuck because it had acquired momentum," Rogers says.

Earth Day has also grown well past its original founding organizers' vision because no organization tightly controls all Earth Day events. Earth Day is "promoted and shaped" by the Earth Day Network, Rogers says, but they let each local group of volunteers create their own events, says the organization's president.

"For example, there were 1,200 Earth Day events registered online in India this year," she says. "EDN did not 'own' them, nor did we directly organize the vast majority of them; we created a context within which local groups felt supported when they put together their own events on the issues that most resonated with them."

No matter their origins, all of these eco-themed holidays are occasions to make a difference in the world. So put a few environmental dates on your calendar and keep celebrating the environment year-round. [/skipwords]